Although deficits in social communication are considered primary in autism spectrum disorders (ASD), recent evidence suggests that motor impairments also constitute a prominent component of the ASD behavioral profile. Interest in the identification of behavioral markers of ASD in infancy has recently led to a number of prospective, longitudinal studies of infants known to be at elevated risk for ASD and other developmental delays (High-Risk infants; HR). Despite the growing literature on motor concerns in ASD, relatively little attention has been devoted to the early development of motor skills in HR infants. In addition, there is wide variability in the outcomes of HR infants at age 3, and it is possible that variation in motor ability may be related to individual differences in developmental outcomes in other domains (e.g. social communication, language). This research is designed to examine fine motor and object manipulation skills in HR and comparison infants with no such risk (Low Risk infants; LR) between the ages of 12 and 36 months. The approach taken is innovative because it involves the application of newly-developed, technologically sophisticated sensor technology designed for use in unstructured settings in combination with longitudinal behavioral observation to collect finely detailed information about the organization and quality of children's movements as they perform three motor tasks at varying levels of difficulty. Supplemented by standardized motor assessments, these data will support the analysis of fine motor and object manipulation abilities in a much more subtle and sophisticated fashion than has heretofore been possible. Twenty HR infants already being followed from 5 to 36 months as part of a larger study and 20 LR infants will be observed at home at ages 12, 14, 18, 24, and 36 months as they perform motor tasks that involve reaching for, transporting, and placing an object at a target location. An additional cross-sectional group of 50 children, 10 at each age listed above, will also participate. Kinematic data will be collected via lightweight sensorized wristbands and sensors embedded in the objects. Analyses will focus on overall risk group differences, on change in the kinematic and behavioral variables as a function of task difficulty and age, and on group by difficulty interactions at varying ages. These will be used to evaluate developmental trajectories and possible developmental delays and impairments in the motor skill of HR children, to examine the relation between motor skills and delays exhibited by HR children in other developmental domains, and to provide preliminary information about kinematic and behavioral signatures that may be related to an eventual diagnosis of ASD. PUBLIC HEALTH RELEVANCE: The recent rapid increase in diagnosis of Autism Spectrum Disorders makes it imperative that we learn more about the early development of children at high risk for ASD. Because motor impairments are common in older children with ASD, and because infants at risk for ASD often exhibit early motor delays, the research will focus on the early development of motor skills in at-risk infants and relate this information to later developmental outcomes. To do this, a novel movement measurement technology will be employed together with detailed behavioral observations of at-risk and comparison low-risk children as they engage in a series of naturalistic motor tasks between the ages of 12 and 36 months.